Texas equine producers, veterinarians and livestock health officials
have become increasingly concerned about Equine Viral Arteritis (EVA),
which has been detected in New Mexico and Utah this year. A viral disease
of horses, donkeys, and other equine animals, EVA causes mares to abort,
can cause mild to severe respiratory disease in some horses and may also
cause some stallions to become chronically infected and shed the virus
in semen. While EVA has been encountered rarely and is not a reportable
disease in Texas, regulations have been implemented in some states, including
Kentucky, New York and Colorado.

While some infected equine exhibit no signs of disease, owners should
be alert and notify their accredited private veterinary practitioner if
horses or foals develop signs of EVA, including fever, depression, diarrhea,
coughing or nasal discharge, or swelling of the legs, body or head. Laboratory
testing is necessary to confirm a diagnosis, as other equine diseases
can present similar clinical signs.

“EVA is not currently a reportable disease in Texas,” said
Dr. Bob Hillman, Texas’ state veterinarian and head of the Texas
Animal Health Commission (TAHC), the state’s livestock and poultry
health regulatory agency. “However, we urge veterinarians and horse
owners to report suspected and confirmed cases of EVA to the TAHC to ensure
we have the most accurate picture of the disease in the state and can
provide up-to-date information to veterinarians and equine owners.”

Horses can be infected by inhaling the equine arteritis virus, through
natural service of a mare by a carrier stallion, artificial insemination
of a mare with semen from a carrier stallion, or by being exposed to bedding
or other objects contaminated with the virus. Stallions that shed the
equine arteritis virus in their semen can infect unvaccinated mares, causing
a respiratory disease and abortion. Acutely infected horses spread the
infection to other horses via the respiratory route. A pregnant mare may
also be infected through contact with acutely infected horses and may
abort. Cleaning and disinfection of stalls, trailers and equipment can
reduce the risk of EVA exposure.

“Know the EVA status of stallions, semen shipments and mares before
they are introduced onto your farm. Consult your accredited private veterinary
practitioner about vaccination protocols for brood mares, stallions and
colt foals, and ensure that good biosecurity measures are followed,”
said Dr. Hillman.

“If you are shipping breeding horses out of state, check to determine
the entry requirements of the receiving state and allow time to comply
with any testing, vaccination or isolation requirements. Many breeding
farms have implemented ‘best management’ practices, testing
and vaccination procedures to prevent the introduction or spread of EVA.
Before delivering mares to farms for breeding, owners should contact the
facility managers to determine what testing and vaccination procedures
must be met.”

“Although only supportive treatment can be provided, most affected
mares, geldings or sexually immature stallions will eliminate the virus
and recover,” said Dr. Hillman. “Sexually mature stallions,
however, can become carriers of the disease and shed the virus for long
periods. Shedding stallions should be isolated and bred only to vaccinated
mares.”

“It is very important to have breeding horses tested, and if appropriate,
vaccinated prior to the breeding season. After vaccination, stallions
and mares should be withheld from breeding for at least 28 or 21 days,
respectively. Vaccinated horses also must be maintained away from pregnant
mares for at least 28 days,” he said. “EVA vaccine may be
acquired only by veterinarians, with prior TAHC approval.”

Additionally, mares vaccinated for the first time and bred to a carrier
stallion should be isolated from other equine for 21 days after breeding.
Owners of breeding horses considering vaccination should consult their
veterinarians if the horse may also be shipped in interstate or international
commerce. A specific pre-vaccination protocol to assure the horse was
test-negative prior to vaccination may be required, because vaccinated
horses will test positive for the disease.

“Several horse breeders and a number of equine veterinarians have
contacted the TAHC about EVA and to urge Texas equine producers to take
all necessary precautions to prevent establishing EVA in Texas horses,”
said Dr. Hillman. “Equine producers and veterinarians believe this
disease can be handled through judicious application of best management
and biosecurity practices, coupled with appropriate use of testing and
vaccination of breeding animals.”

“The current EVA situation will be reported to TAHC commissioners
at their meeting Tuesday, December 5, in Austin,” he said. “Development
of EVA rules is not anticipated at this time. Horse breeders are urged
to work with their veterinarians to institute best management and biosecurity
practices immediately to protect their investment and the health of their
animals. EVA can be prevented and controlled by sound management practices
and selective use of the EVA vaccine.”